MOTOBRICK.COM
TECHNICAL MOTOBRICK WRENCHING In Remembrance of Inge K. => The Motobrick Workshop => Topic started by: HamMan on October 23, 2023, 06:52:36 PM
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Hey all, back at it after enjoying the bike for a bit. Went for a ride and noticed it was a little tricky to start. Finally it caught and off I went. About 1 mile down the road it stopped and wouldn’t start.
Got it home and noticed fuel filling the exhaust!
Pump is whirring when button pushed.
Read about temp sensor so replaced that and no cure.
Replaced with new plugs as well.
Has great spark
Appears to be great fuel pressure. Don’t currently have a gauge to test
Now it will only catch and run with the fuel pump unplugged. The split second I plug it in when running it just immediately shuts off. So, almost electrical seeming idk 🤷.
Even if I barley touch the fuel pump fuse back into its socket it also dies immediately. This is with the pump plugged in.
Possibly Hall effect? MAF sensor? Looks I may need to check for shorts circuits.
Thanks all
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simple stuff first, injector(s) stuck open?
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Appears to be great fuel pressure.
What is the visual difference between "great" fuel pressure that creates good ignition and "excessive" fuel pressure that causes an engine to flood?
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Pull out the spark plugs, are they all wet???? If so it could still be a faulty temp sensor/ sensor wiring. One wire from the temp sensor goes through a connector under the tank and we have encountered a break there. It then goes to the Temperature Sensor Switch Unit. The other wire goes to the Fuel Injection Control Unit we have also seen a dirty connector there. If only one or two wet then pursue the Chaos theory.
Regards Martin.
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Thanks all for the inputs. I currently have the tank off and will check the wiring. I am running an aftermarket speedo and junction box from Tenet. It was a direct plug and play though other than the fuel gauge input wire I had to tap into the original harness for that.
All 3 plugs are wet and when the pump is plugged in and you try to start it, as mentioned fuel drips out of the exhaust where it meets the silencer. I have an aftermarket silencer as well.
I read through this fellows issue which sounded like dead on to my issue. The guy who started the thread never came back to say if he fixed it or not but another member replaced his ECU and it solved his issues. I’ll check first to see if the injectors are stuck open and I’ll check the wiring of the temp sensor. I see it goes from the sensor and snakes into the injector wiring harness. I’ll also remove all grounds and clean them and clean all the terminals connectors and report back.
http://www.motobrick.com/index.php?PHPSESSID=a0ff959fa052eb4491db722ccb6d834c&topic=7346.25
I did have the injectors out a few months back as the bike had sat for many years but started and ran fine. I pulled them to clean all the old junk and nasty stuff out and cleaned up the fuel rail as it looked like $hit.
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Temp sensor troubleshooting:
http://www.kbikeparts.com/classickbikes.com/ckb.tech/0.ckb.tech.files/tempsensor/tempsensor.htm
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At the risk of sounding like a broken record, one quick check is to use a screwdriver as a stethoscope on the injectors, they should be making a ticking sound.
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Updates! Bike is back to running. Haven’t test rode it yet but starts, idles and revs up beautifully.
I found quite a bit of terminals had some corrosion and a somehow a bit of water collected inside the jetronic box probably shorting circuiting or grounding out something. Who the hell knows. The box isn’t in the stock location as the bike has been Cafe’d. I opened the box, let it air dry for 3 days. Cleaned it all up and finished cleaning up terminals and connectors. Fresh gas, oil and boom fired right up. So, next up is make a splash shield for the box. I put a bit of extra silicon around the two halves as well upon reassembly.
So of course water in there could have been the main culprit, plus a new temp sensor, cleaned terminals and such. All things combined we should be back in business.
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Thanks for the update! icon_cheers
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Order the cake but it's too early to start the party. :laughing4-giggles:
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I love cake though 🤪